Polyurethanes and related polyureas are used in a wide variety of applications, including fibers (particularly the elastic type), adhesives, coatings, elastomers, and flexible and rigid foams. A number of methods have been employed to prepare polyurethanes and polyureas. For example, in industrial applications, polyurethane-polyurea polymers are typically synthesized by the condensation reaction of a polyisocyanate, such as diphenylmethane diisocyanate, and a resin that includes a hydroxyl-containing material. Resins may also include linear polyesters, polyethers containing hydroxyl groups, amine-substituted aromatics, and aliphatic amines. The resulting polyurethane-polyurea polymer provides resistance to abrasion, weathering, and organic solvents and may be utilized in a variety of industrial applications as a sealant, caulking agent, or lining, for example.
It has been found, however, that the existing polyurethane-polyurea polymers are not necessarily successful in aggressive environments. The existing polyurethane-polyurea polymers exhibit insufficient chemical and/or permeability resistance when placed into prolonged contact with organic reagents such as fuels and organic solvents. Accordingly, further improvements are warranted in the preparation of polyurethane-polyurea polymers.